1. Field of the Invention
The present invention relates in general to a fluid motor for converting fluid pressure to rotational motivation, and capable of pumping fluid when rotational motivation is applied to the motor, and, more specifically, to a fluid pressure motor with pumping capabilities utilizing a cam actuated vane.
2. Description of the Prior Art
Motors for converting fluid pressure to rotational motivation are generally known in the art. Two types of such motors are the turbine motor and the vane motor. A turbine motor includes a circular shell, having an inlet on its circumference and an exhaust at its center. A plurality of radially-extending, curved fins is provided within the shell. Pressurized fluid is provided into the shell through the inlet. The pressurized fluid pushes outward against the curved fins to rotate the fins before exiting through the exhaust port at the center of the circular shell.
One drawback of turbine motors is the high operating speeds typically required to develop sufficient torque. High operating speeds also make turbine motors susceptible to contamination. If particulate matter enters a turbine motor, the vanes of the turbine motor strike the particulate matter at high speed, causing damage to the vanes. Due to the high speed, even very small particulate matter can erode or destroy a vane. An additional drawback of the turbine motor is its inefficiency at low speeds. Turbine motors typically cannot start against an applied load. If a load were applied to a turbine motor before the vanes began to rotate, pressurized fluid applied through the inlet would simply exit directly out the exhaust port without rotating the vanes. Additionally, turbine motors are incapable of generating reverse rotational motion. If fluid were provided to the motor in a reverse direction, the vanes would still rotate in the same direction. Accordingly, a transmission is required to operate turbine motors efficiently at various speeds and reversing gears are required to generate reverse torque using a turbine motor.
Like a turbine motor, a vane motor has a plurality of radially-extending vanes. Unlike a turbine motor, however, the vanes of a vane motor are straight and extensible in relation to a center cylinder. The vanes of a vane motor are received in slots provided in the center cylinder. The vanes and center cylinder are provided within an elliptical shell. Fluid is supplied into the shell through a fluid input provided along the circumference of the shell. The fluid presses against the vanes and propels the center cylinder before exiting from an exhaust also provided along the circumference of the shell. Rotation of the center cylinder throws the vanes outward against the interior walls of the shell. Since the exterior shell is elliptical, and the vanes extend to the exterior shell, more of the vanes are exposed as the vanes pass the drive side of the exterior shell than is exposed as the vanes pass the recovery side of the exterior shell.
As the vanes pass by the drive side of the shell, the walls of the shell force the vanes into the slots. Conversely, as the vanes pass the recovery side of the shell, the vanes are thrown outward to their full extension. This extension and retraction of the vanes reduces the exposed surface area of the vanes to reduce undesired counter thrust. The vanes are, however, at least partially extended throughout the rotation. A certain portion of the fluid, therefore, presses against the vanes, imparting undesired counter force. Accordingly, a certain amount of fluid pressure goes toward applying force to the vanes in the reverse direction. Not only is this counter force unavailable to drive the vanes in the desired direction, but the counter force makes driving the vanes more difficult.
Accordingly, vane motors are a relatively inefficient conversion of fluid pressure to rotational motion. Additionally, the vanes rub against the exterior shell, reducing the lifespan of the vanes and typically requiring continuous lubrication. Operating vane motor at high speeds will often reduce the lifespan of the vanes even further. Although vane motors can produce torque at low speeds, unlike turbine motors, vane motors have a relatively narrow band of fluid pressures over which the most efficient torque is obtained. Due to this narrow band of efficiency, vane motors also must be used in conjunction with a transmission to obtain efficient rotational motion at multiple shaft speeds.
Prior art fluid pressure rotational motors typically have an outer shell containing a plurality of vanes rotating about an axis at the center of the shell. Due to their design, prior art motors have numerous unique disadvantages, as well as the common disadvantages of inefficiency of operation and a narrow band of fluid pressures over which the most efficient torque is produced. It would be desirable to provide a fluid motor with an efficient production of torque over a wide range of fluid pressures, to provide not only a stable rotational torque, but also to eliminate the need for a transmission and a reverse gear. It would also be desirable to provide a long-wearing motor capable of withstanding vane contact with small amounts of particulate matter. The difficulties encountered in the prior art discussed hereinabove are substantially eliminated by the present invention.